As a continuation and expansion of prior and ongoing studies, the primary objective of the project is to contribute to the body of scientific information concerning the comparative anatomy (morphology, histology, cytology) and evolution of the vertebrate labyrinth. Methodology will include techniques of light microscopy, SEM and TEM. Specific investigations will include: (1) extension of a developmental study of the basilar papilla in the Pekin duck; (2) a study of the distribution of gap junctions between sensory and supporting cells in a selected series of reptiles; (3) a cytochemical study of basally infolded cells in the labyrinth of Anolis; and (4) a tracer study of possible membrane recycling and synaptic vesicle formation at afferent synaptic sites in the basilar papilla of Anolis.